Some vehicles are provided with automatic stop/start controllers so as to reduce fuel consumption by the vehicles' engines. The automatic stop/start controller automatically stops the engine when an automatic stop condition, e.g., an accelerator pedal is not depressed while the engine is operating, is satisfied, and automatically starts the engine when an automatic start condition, e.g., the start operation occurs while the engine is automatically stopped, is satisfied. (See JP Laid-Open No. 2002-106380.)
As regards a conventional automatic stop/start controller for the engine, it is present in the vehicle to permit the engine to automatically stop and restart to enhance fuel economy.
In a conventional vehicle provided with an automatic transmission, an electrically-powered pump generates an oil pressure while the engine is automatically stopped, and is controlled to maintain low pressure during automatic engine stop and high pressure at engine restart. Thus, the required oil pressure is maintained while restricting electric power consumed by the electrical pump.
Although the power consumption is minimized to maintain low pressure during automatic engine stop, the electrical pump continuously consumes electric power during automatic engine stop. There is thus still room for improvement in fuel consumption.
If the electric pump is eliminated, the fuel economy is improved by eliminating the electric power consumed by the electric pump. However, the oil pressure cannot be maintained during the automatic engine stop, so that the oil pressure is then generated at engine restart and delays occur until frictional engaging elements in the automatic transmission are engaged.
As a result, if the accelerator pedal is depressed before the frictional engaging elements are engaged, the engaging elements will be engaged after the engine speed is increased sharply. This causes shock at engagement of the elements, or deteriorates the durability of the automatic transmission.